1. Field of the Invention
The present invention relates to the field of integrated circuit technology and in particular to a copper diffusion barrier and a method of forming the same.
2. Background of the Invention
When forming a copper portion in an insulating layer of an integrated circuit structure, for example a copper interconnect surrounded with an insulating layer, it is normal to provide a barrier between the copper and the insulating material to prevent diffusion of the copper during the lifetime of the integrated circuit. Generally, after a trench for the contact has been formed in the insulating layer, a barrier layer is deposited lining the trench. Materials such as tantalum or tantalum nitride are often used to form the barrier. This barrier is for example applied in a first deposition chamber using PVD (physical vapour deposition). The barrier is then covered by a copper seed layer in a second deposition chamber, also using PVD. The copper for forming the contact is then deposited in a further chamber, generally using ECD (Electrochemical deposition).
In some cases it is not possible to deposit the copper seed layer in a continuous layer. If the copper seed layer comprises gaps, this often results in voids forming in the copper contact, which generally add to the resistance of the contact, and can lead to complete failure of the contact.